Bentonite from
USA | |
| Bentonite is described on an interpretive sign in Badlands National Park. |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| Roberts, Willard Lincoln, Rapp, George Jr. (1965) Mineralogy of the Black Hills. Bulletin 18. South Dakota School of Mines and Technology |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |